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Effects of protein synthesis inhibitors on sleep and seizure susceptibility in kindled and nonkindled cats
BEHAVIORAL AND NEURAL BIOLOGY
35, 432-437 (1982)
BRIEF REPORT Effects of Protein Synthesis Inhibitors on Sleep and Seizure Susceptibility in Kindled and Nonkindled Cats 1 S. SCOTT BOWERSOX2 AND
M. N.
SHOUSE
Neurophysiology Laboratory, VA Medical Center, Sepulveda, California 91343; and Brain Research Institute, University of California, Los Angeles, California 90025 This study examined the effects of protein synthesis inhibitors on sleep and seizure susceptibility in kindled and nonkindled cats. Animals were treated with chloramphenicol or its congener, thiamphenicol (150 mg/kg, oral), at 12-hr intervals over a 30-hr period. State pattern variables were monitored continuously during the first 24 hr. At 30 hr, animals were administered convulsive doses of monomethylhydrazine (10 mg/kg, ip), and seizure latencies, measured from the time of drug injection to the onset of tonic-clonic convulsions, were determined. Circadian state pattern percentages for untreated kindled and nonkindled animals agreed with values reported in previous studies. Rapid eye movement (REM) sleep was significantly reduced in animals treated with chloramphenicol, but was unaffected by thiamphenicol administration. Seizure latencies were unaltered in nonkindled cats pretreated with protein synthesis inhibitors: however, seizure susceptibility in kindled animals was significantly enhanced following chloramphenicol administration. Thus, protein synthesis inhibition reduced seizure thresholds only when it was associated with the suppression of REM sleep in animals predisposed to seizures. This finding suggested that the functional stability of neural systems is, to some extent, dependent upon REM related anabolic activity.
Rates of brain protein synthesis, normally highest during sleep periods dominated by the rapid-eye-movement(REM) phase (Brodsky, Gusatinsky, Kogan, & Nechaeva, 1974; Drucker-Colin, Spanis, Cotman, & McGaugh, 1975), are significantly attenuated by REM sleep deprivation (DruckerColin, 1981; Lambrey-Sakai, 1969). For this reason, it was recently sugThis research was supported by the Veterans Administration and U.S. Air Force Contract F33 615-79-C-0506 and U.S. Public Health Service Grant 1R01 NS 16152-01. 2 To whom correspondence and reprint requests should be sent at: Sleep Research Center, Department of Psychiatry (TD-114), Stanford University School of Medicine, Stanford, Calif. 94305. 432 0163 - 1047/82/080432-06502.00/0 Copyright © 1982 by Academic Press, Inc. All rights of reproduction in any form reserved.
PROTEIN SYNTHESIS INHIBITION AND SEIZURES
433
gested that the increase in central nervous system (CNS) excitability commonly seen in association with sustained REM sleep loss results from disturbances of brain protein anabolism (Drucker-Colfn, 1981). The current study considered this possibility by comparing the effects of protein synthesis inhibitors (PSI), chloramphenicol and thiamphenicol, on sleep and seizure susceptibility in kindled and nonkindled cats. Twelve healthy adult cats of either sex, weighing between 2.7 and 4.7 kg, were studied. All were surgically prepared, under pentobarbital anesthetic (Nembutal, 35 mg/kg), for chronic monitoring of electroencephalograms (EEG), eye movements (EOG), and electromyelograms (EMG) utilizing standard procedures described in detail elsewhere (Ursin & Sterman, 1981). Briefly, small stainless-steel screw electrodes were threaded into the eye orbit within the frontal sinus (EOG) and into the skull over sensorimotor and occipital cortices (EEG). Flexible, braided-steel wires were implanted into the nuchal musculature bilaterally (EMG). Tripolar, stainless-steel electrodes with staggered tips were inserted into the lateral geniculate nucleus (A: 6, L: 10.5, H: 2.5) to monitor ponto-geniculooccipital (PGO) spikes and into the basolateral amygdala (A: 11, L: 9.0, H: -5.5) for kindling. After a minimum 2-week recovery period, seven animals received daily electrical stimulation of the amygdala until stable Stage 6 seizures were elicited. The remaining five animals were handled daily but did not receive amygdala stimulation. Both kindled and nonkindled animals sustained multiple, prolonged polygraphic recordings and were therefore well adapted to the recording chamber. The kindling and control procedures, both of which have been described previously (Shouse & Sterman, 1981), were completed at least 1 month before the present experiment began. Sleep state patterns and seizure susceptibility were documented under three experimental conditions: (1) an untreated baseline condition, (2) following pretreatment with chloramphenicol (CAP), and (3) following pretreatment with thiamphenicol (TAP), The experimental design was a within-subjects paradigm in which I month intervened between each of the three consecutive experimental conditions. Further, the order of exposure to CAP and TAP was counterbalanced except as noted below. PSI pretreatment trials consisted of the oral administration of 150 mg/kg of either CAP or TAP at 12-hr intervals over a 30-hr period, beginning between 0800 and 0900 hr. State pattern data were collected continuously on a Grass Model 78B polygraph during the first 24 hr of each trial. Six hours later, animals were exposed to a convulsive dosage (10 mg/kg, ip) of the toxic hydrazide derivative monomethylhydrazine (MMH). Seizure latencies were measured from the time of drug injection to the onset of generalized tonic-clonic convulsions. Seizures were terminated with an
434
BOWERSOX AND SHOUSE
anesthetic dose of pentobarbital sodium, which was administered during the tonic phase. Baseline trials were conducted under identical conditions except that there was no pretreatment with protein synthesis inhibitors. It was intended to employ the modified counterbalanced design uniformly in eight animals, four kindled and four nonkindled. This was not possible, however, because four animals, three kindled and one nonkindled, died during recovery from MMH-induced convulsions following PSI pretreatment. The high incidence of death may be attributed to untoward drug interactions between PSI and Nembutal, because animals died long after M M H seizures but before recovery from anesthesia. Thus, the four cats that survived PSI pretreatment experienced the withinsubjects design as planned, with two cats receiving CAP first and two receiving TAP first. Cats that died were replaced in the final PSI trial by the remaining four animals in the study, which therefore experienced one CAP or TAP trial independently. This unfortunate development, however, should not detract from the findings because studies comparing seizure thresholds following single and multiple exposures to MMH indicate no differences (Shouse, 1982). Moreover, animals as well adapted as these show no differences in state variables over time (Shouse & Sterman, 1981). Polygraphic records were scored according to standard criteria (Ursin & Sterman, 1981), and the percentage of time spent in waking and sleep states was calculated for animals in each condition. Alert waking and drowsy states were combined for the "waking" designation; "slow-wave sleep" included both light and deep slow-wave sleep stages. Percentage distributions for each group are shown in Fig. 1. A one-way analysis of variance was used for tests of statistical significance. Individual group differences were evaluated by multiple comparison t tests. In the untreated condition, the percentage of time spent in waking, slow-wave sleep, and REM sleep for nonkindled animals averaged 37.8 + 2.4, 48.8 -+ 3.9, and 13.4 _+ 3.1, respectively. These values agreed closely with previously reported findings (Sterman, Knauss, Lehman, & Clemente, 1965). Corresponding values for kindled animals were 60.4 _+ 10.2, 27.8 +_ 7.0, and 11.8 -+ 3.5. Differences with respect to waking and slow-wave sleep percentages were statistically significant (waking: t(6) = 4.3, p < .01 ; slow-wave sleep: t(6) = - 5.2, p < .01), corroborating earlier findings which indicated a sustained facilitation of waking and suppression of slow-wave sleep with amygdala kindling (Shouse & Sterman, 1981). Chloramphenicol treatment (150 mg/kg) led to highly significant reductions of REM sleep in all animals (kindled--F(2, 9) = 14.5, p < .01, untreated vs CAP: t(6) = 5.0, p < .01; nonkindled--F(2, 9) = 12.4, p < .01, untreated vs CAP: t(6) = 4.8, p < .01). Mean values in kindled and nonkindled animals declined from 11.8 +_ 3.5 and 13.4 + 3.1, re-
435
PROTEIN SYNTHESIS INHIBITION AND SEIZURES NON-KINDLED
KINDLED
CONTROL
CHLORAMPHENICOL (150 mg/kg)
3*2%
Fa%
28
(t50 mg/kg)
E ~ WAKING ]SLOW-WAVE SLEEP
~
REM
FIG. 1. Circadian state pattern percentages for kindled and nonkindled cats of three groups. Shown are group means and standard deviations.
spectively, to 1.8 _+ 1.7 and 3.2 -+ 2.8. Chloramphenicol did not alter waking and slow-wave sleep percentages in the nonkindled cats; in the kindled animals, however, REM sleep reductions were accompanied by significant increases in slow-wave sleep (F(2, 9) = 8.5, p < .02, untreated vs CAP: t(6) = - 3.2, p < .05). Thiamphenicol, adminstered at the same dosage and by the same route, failed to suppress R E M sleep; in fact, in kindled animals total sleep time increased significantly from 39.7 _+ 10.2 to 61.7 + 10.0 (F(2, 9) = 7.0, p < .05, untreated vs TAP: t(6) = - 3 . 1 , p < .05). M M H seizure latency values for the untreated group were comparable with those previously reported for kindled and nonkindled cats (Shouse, 1981; Sterman, 1976). Values for nonkindled animals ranged from 60 to 73 min with a mean latency of 64 + 6.1 rain. Latencies were more variable in kindled cats, ranging from 66 to 100 min with an average of 75.5 _+ 16.3 rain. Pretreatment with PSIs did not appreciably alter seizure latencies in nonkindled cats; values ranged from 55 to 83 min (X = 72.5 _+ 12.4) in the T A P condition and from 55 to 79 min (J( = 64.5 + 11.3) in the CAP condition. Latencies for kindled animals treated with TAP ranged from 48 to 120 min O~ = 82.8 + 30.1). The TAP group mean was comparable to that for the untreated condition. Seizure latencies in kindled animals were considerably shortened following CAP treatment, ranging from 46 to 55 min (J£ = 50.5 _+ 4.2). Statistical comparisons
436
BOWERSOX AND SHOUSE
confirmed that the CAP group mean was lower than that of either the untreated or TAP treatment groups (p < .05) (Fig. 2). The MMH response is normally characterized by a sequence of symptoms which begins with piloerection or hyperventilation, progresses through emesis, salivation, panting, hyperactivity, and myoclonic twitching, and then culminates in generalized tonic-clonic convulsions (Sterman, 1976). Kindled animals pretreated with CAP did not exhibit this sequence. Although early signs of MMH intoxication--namely, piloerection, hyperventilation, and emesis--regularly occurred, prodromal motor behaviors were absent. Instead, seizures erupted suddenly during periods of quiescence. Moreover, the sequence of convulsive motor behaviors replicated that induced by the kindling process. This suggested that previous kindling sensitized animals to subsequent seizure induction. Results of this investigation confirmed previous findings which showed that chloramphenicol suppressed REM sleep in the cat while thiamphenicol, a CAP congener with similar pharmacologic properties, was ineffective (Drucker-Colin, 1981; Petitjean, Buda, Janin, David, & Jouvet, 1979). MMH seizure responses were facilitated by CAP pretreatment in kindled animals, suggesting a relation between PSI-induced REM sleep loss and CNS activation. If REM sleep deficits alone were responsible for increasing neural excitability, however, one might have expected both kindled and nonkindled cats to show greater susceptibility to MMH A
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CAP
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CONTROL
CAP TAP (150mg/kg) (150 mo/kg) KINDLED
P
FXG. 2. Comparisons of M M H seizure latencies for three groups of kindled and nonkindled cats. *p < .05 versus untreated and T A P treatment groups ( W i l c o x o n - M a n n - W h i t n e y rank sum test).
PROTEIN SYNTHESIS INHIBITION AND SEIZURES
437
following CAP administration. The fact that seizure latencies were not shortened in nonkindled animals raises an interesting possibility; that is, the period of PSI treatment and associated REM sleep loss (30 hr) may have been sufficient to produce measurable changes in seizure thresholds only in animals already disposed toward seizures. The differential effects of PSI on M M H seizure latency are not readily amenable to alternative explanations, such as inhibition of protein synthesis in peripheral tissues, because these changes were equivalent in both kindled and nonkindled animals. In summary, results of this investigation showed that protein synthesis inhibition was ineffective in reducing seizure thresholds unless it was associated with the suppression of REM sleep in animals predisposed toward seizures. Even though the integrity of REM sleep alone was not a critical determinant of seizure susceptibility, it may be concluded that the functional stability of neural systems is to some extent dependent upon REM-related anabolic activity. REFERENCES Brodsky, W., Gusatinsky, N. V.. Kogan, A. B., & Nechaeva, N. V. (1974). Variations in the intensity of 3H leucine incorporation into proteins during slow wave and paradoxical phases of natural sleep in the cat associative cortex. Doklady Akademii Nauk SSSR, 215, 748-750. Drucker-Colfn, R. R., Spanis, C, W., Cotman, C. W., & McGaugh~ J. L. (1975). Changes in protein in perfusates of freely moving cats: Relation to behavioral state. Science, 187, 963-965. Drucker-Colfn, R. R. (1981). Neuroproteins, brain excitability, and REM sleep. In W. Fishbein (Ed.), Sleep, Dreams, and Memory: Advances in Sleep Research, pp. 73-93. Flushing. N.Y.: Spectrum. Lambrey-Sakai, F. (1969). Incorporation d'un melange d'acides amines trities dans les proteines cerebrales du rat. en rapport avec la privacion de sommeil, p. 87. These de Biochemie, Universite de Lyon. Petitjean, F., Buda, C., Janin, M., David, M., & Jouvet, M. (1979). Effets du chloramphenicol sur le sommeil du chat--Comparaison avec le thiamphenicol, l'erythromycine et l'oxytetracycline. Psychopharmacology, 66, 147-153. Shouse, M. N. (1982). Acute effect of pyridoxine hydrochloride on monomethylhydrazine seizure latency and amygdaloid kindled seizure thresholds in cats. Experimental Neurology, 75, 79-88. Shouse, M. N., & Sterman, M. B. (1981). Sleep and kindling: I1. Effects of generalized seizure induction. Experimental Neurology, 71, 563-580. Sterman, M. B. (1976). Effects of brain surgery and EEG operant conditioning on seizure latency following monomethylhydrazine intoxication in the cat. Experimental Neurology, 50, 757-765. Sterman, M. B., Knauss, T., Lehman. D.. & Clemente. C. D. (1965). Circadian sleep and waking patterns in the laboratory cat. Electroencephalography and Clinical Neurophysiology, 19, 509-517. Ursin, R., & Sterman, M. B. (1981). A Manual for Recording and Scoring of Sleep Stages in the Cat. Los Angeles: Brain Information Service. UCLA.
35, 432-437 (1982)
BRIEF REPORT Effects of Protein Synthesis Inhibitors on Sleep and Seizure Susceptibility in Kindled and Nonkindled Cats 1 S. SCOTT BOWERSOX2 AND
M. N.
SHOUSE
Neurophysiology Laboratory, VA Medical Center, Sepulveda, California 91343; and Brain Research Institute, University of California, Los Angeles, California 90025 This study examined the effects of protein synthesis inhibitors on sleep and seizure susceptibility in kindled and nonkindled cats. Animals were treated with chloramphenicol or its congener, thiamphenicol (150 mg/kg, oral), at 12-hr intervals over a 30-hr period. State pattern variables were monitored continuously during the first 24 hr. At 30 hr, animals were administered convulsive doses of monomethylhydrazine (10 mg/kg, ip), and seizure latencies, measured from the time of drug injection to the onset of tonic-clonic convulsions, were determined. Circadian state pattern percentages for untreated kindled and nonkindled animals agreed with values reported in previous studies. Rapid eye movement (REM) sleep was significantly reduced in animals treated with chloramphenicol, but was unaffected by thiamphenicol administration. Seizure latencies were unaltered in nonkindled cats pretreated with protein synthesis inhibitors: however, seizure susceptibility in kindled animals was significantly enhanced following chloramphenicol administration. Thus, protein synthesis inhibition reduced seizure thresholds only when it was associated with the suppression of REM sleep in animals predisposed to seizures. This finding suggested that the functional stability of neural systems is, to some extent, dependent upon REM related anabolic activity.
Rates of brain protein synthesis, normally highest during sleep periods dominated by the rapid-eye-movement(REM) phase (Brodsky, Gusatinsky, Kogan, & Nechaeva, 1974; Drucker-Colin, Spanis, Cotman, & McGaugh, 1975), are significantly attenuated by REM sleep deprivation (DruckerColin, 1981; Lambrey-Sakai, 1969). For this reason, it was recently sugThis research was supported by the Veterans Administration and U.S. Air Force Contract F33 615-79-C-0506 and U.S. Public Health Service Grant 1R01 NS 16152-01. 2 To whom correspondence and reprint requests should be sent at: Sleep Research Center, Department of Psychiatry (TD-114), Stanford University School of Medicine, Stanford, Calif. 94305. 432 0163 - 1047/82/080432-06502.00/0 Copyright © 1982 by Academic Press, Inc. All rights of reproduction in any form reserved.
PROTEIN SYNTHESIS INHIBITION AND SEIZURES
433
gested that the increase in central nervous system (CNS) excitability commonly seen in association with sustained REM sleep loss results from disturbances of brain protein anabolism (Drucker-Colfn, 1981). The current study considered this possibility by comparing the effects of protein synthesis inhibitors (PSI), chloramphenicol and thiamphenicol, on sleep and seizure susceptibility in kindled and nonkindled cats. Twelve healthy adult cats of either sex, weighing between 2.7 and 4.7 kg, were studied. All were surgically prepared, under pentobarbital anesthetic (Nembutal, 35 mg/kg), for chronic monitoring of electroencephalograms (EEG), eye movements (EOG), and electromyelograms (EMG) utilizing standard procedures described in detail elsewhere (Ursin & Sterman, 1981). Briefly, small stainless-steel screw electrodes were threaded into the eye orbit within the frontal sinus (EOG) and into the skull over sensorimotor and occipital cortices (EEG). Flexible, braided-steel wires were implanted into the nuchal musculature bilaterally (EMG). Tripolar, stainless-steel electrodes with staggered tips were inserted into the lateral geniculate nucleus (A: 6, L: 10.5, H: 2.5) to monitor ponto-geniculooccipital (PGO) spikes and into the basolateral amygdala (A: 11, L: 9.0, H: -5.5) for kindling. After a minimum 2-week recovery period, seven animals received daily electrical stimulation of the amygdala until stable Stage 6 seizures were elicited. The remaining five animals were handled daily but did not receive amygdala stimulation. Both kindled and nonkindled animals sustained multiple, prolonged polygraphic recordings and were therefore well adapted to the recording chamber. The kindling and control procedures, both of which have been described previously (Shouse & Sterman, 1981), were completed at least 1 month before the present experiment began. Sleep state patterns and seizure susceptibility were documented under three experimental conditions: (1) an untreated baseline condition, (2) following pretreatment with chloramphenicol (CAP), and (3) following pretreatment with thiamphenicol (TAP), The experimental design was a within-subjects paradigm in which I month intervened between each of the three consecutive experimental conditions. Further, the order of exposure to CAP and TAP was counterbalanced except as noted below. PSI pretreatment trials consisted of the oral administration of 150 mg/kg of either CAP or TAP at 12-hr intervals over a 30-hr period, beginning between 0800 and 0900 hr. State pattern data were collected continuously on a Grass Model 78B polygraph during the first 24 hr of each trial. Six hours later, animals were exposed to a convulsive dosage (10 mg/kg, ip) of the toxic hydrazide derivative monomethylhydrazine (MMH). Seizure latencies were measured from the time of drug injection to the onset of generalized tonic-clonic convulsions. Seizures were terminated with an
434
BOWERSOX AND SHOUSE
anesthetic dose of pentobarbital sodium, which was administered during the tonic phase. Baseline trials were conducted under identical conditions except that there was no pretreatment with protein synthesis inhibitors. It was intended to employ the modified counterbalanced design uniformly in eight animals, four kindled and four nonkindled. This was not possible, however, because four animals, three kindled and one nonkindled, died during recovery from MMH-induced convulsions following PSI pretreatment. The high incidence of death may be attributed to untoward drug interactions between PSI and Nembutal, because animals died long after M M H seizures but before recovery from anesthesia. Thus, the four cats that survived PSI pretreatment experienced the withinsubjects design as planned, with two cats receiving CAP first and two receiving TAP first. Cats that died were replaced in the final PSI trial by the remaining four animals in the study, which therefore experienced one CAP or TAP trial independently. This unfortunate development, however, should not detract from the findings because studies comparing seizure thresholds following single and multiple exposures to MMH indicate no differences (Shouse, 1982). Moreover, animals as well adapted as these show no differences in state variables over time (Shouse & Sterman, 1981). Polygraphic records were scored according to standard criteria (Ursin & Sterman, 1981), and the percentage of time spent in waking and sleep states was calculated for animals in each condition. Alert waking and drowsy states were combined for the "waking" designation; "slow-wave sleep" included both light and deep slow-wave sleep stages. Percentage distributions for each group are shown in Fig. 1. A one-way analysis of variance was used for tests of statistical significance. Individual group differences were evaluated by multiple comparison t tests. In the untreated condition, the percentage of time spent in waking, slow-wave sleep, and REM sleep for nonkindled animals averaged 37.8 + 2.4, 48.8 -+ 3.9, and 13.4 _+ 3.1, respectively. These values agreed closely with previously reported findings (Sterman, Knauss, Lehman, & Clemente, 1965). Corresponding values for kindled animals were 60.4 _+ 10.2, 27.8 +_ 7.0, and 11.8 -+ 3.5. Differences with respect to waking and slow-wave sleep percentages were statistically significant (waking: t(6) = 4.3, p < .01 ; slow-wave sleep: t(6) = - 5.2, p < .01), corroborating earlier findings which indicated a sustained facilitation of waking and suppression of slow-wave sleep with amygdala kindling (Shouse & Sterman, 1981). Chloramphenicol treatment (150 mg/kg) led to highly significant reductions of REM sleep in all animals (kindled--F(2, 9) = 14.5, p < .01, untreated vs CAP: t(6) = 5.0, p < .01; nonkindled--F(2, 9) = 12.4, p < .01, untreated vs CAP: t(6) = 4.8, p < .01). Mean values in kindled and nonkindled animals declined from 11.8 +_ 3.5 and 13.4 + 3.1, re-
435
PROTEIN SYNTHESIS INHIBITION AND SEIZURES NON-KINDLED
KINDLED
CONTROL
CHLORAMPHENICOL (150 mg/kg)
3*2%
Fa%
28
(t50 mg/kg)
E ~ WAKING ]SLOW-WAVE SLEEP
~
REM
FIG. 1. Circadian state pattern percentages for kindled and nonkindled cats of three groups. Shown are group means and standard deviations.
spectively, to 1.8 _+ 1.7 and 3.2 -+ 2.8. Chloramphenicol did not alter waking and slow-wave sleep percentages in the nonkindled cats; in the kindled animals, however, REM sleep reductions were accompanied by significant increases in slow-wave sleep (F(2, 9) = 8.5, p < .02, untreated vs CAP: t(6) = - 3.2, p < .05). Thiamphenicol, adminstered at the same dosage and by the same route, failed to suppress R E M sleep; in fact, in kindled animals total sleep time increased significantly from 39.7 _+ 10.2 to 61.7 + 10.0 (F(2, 9) = 7.0, p < .05, untreated vs TAP: t(6) = - 3 . 1 , p < .05). M M H seizure latency values for the untreated group were comparable with those previously reported for kindled and nonkindled cats (Shouse, 1981; Sterman, 1976). Values for nonkindled animals ranged from 60 to 73 min with a mean latency of 64 + 6.1 rain. Latencies were more variable in kindled cats, ranging from 66 to 100 min with an average of 75.5 _+ 16.3 rain. Pretreatment with PSIs did not appreciably alter seizure latencies in nonkindled cats; values ranged from 55 to 83 min (X = 72.5 _+ 12.4) in the T A P condition and from 55 to 79 min (J( = 64.5 + 11.3) in the CAP condition. Latencies for kindled animals treated with TAP ranged from 48 to 120 min O~ = 82.8 + 30.1). The TAP group mean was comparable to that for the untreated condition. Seizure latencies in kindled animals were considerably shortened following CAP treatment, ranging from 46 to 55 min (J£ = 50.5 _+ 4.2). Statistical comparisons
436
BOWERSOX AND SHOUSE
confirmed that the CAP group mean was lower than that of either the untreated or TAP treatment groups (p < .05) (Fig. 2). The MMH response is normally characterized by a sequence of symptoms which begins with piloerection or hyperventilation, progresses through emesis, salivation, panting, hyperactivity, and myoclonic twitching, and then culminates in generalized tonic-clonic convulsions (Sterman, 1976). Kindled animals pretreated with CAP did not exhibit this sequence. Although early signs of MMH intoxication--namely, piloerection, hyperventilation, and emesis--regularly occurred, prodromal motor behaviors were absent. Instead, seizures erupted suddenly during periods of quiescence. Moreover, the sequence of convulsive motor behaviors replicated that induced by the kindling process. This suggested that previous kindling sensitized animals to subsequent seizure induction. Results of this investigation confirmed previous findings which showed that chloramphenicol suppressed REM sleep in the cat while thiamphenicol, a CAP congener with similar pharmacologic properties, was ineffective (Drucker-Colin, 1981; Petitjean, Buda, Janin, David, & Jouvet, 1979). MMH seizure responses were facilitated by CAP pretreatment in kindled animals, suggesting a relation between PSI-induced REM sleep loss and CNS activation. If REM sleep deficits alone were responsible for increasing neural excitability, however, one might have expected both kindled and nonkindled cats to show greater susceptibility to MMH A
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CAP
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P
FXG. 2. Comparisons of M M H seizure latencies for three groups of kindled and nonkindled cats. *p < .05 versus untreated and T A P treatment groups ( W i l c o x o n - M a n n - W h i t n e y rank sum test).
PROTEIN SYNTHESIS INHIBITION AND SEIZURES
437
following CAP administration. The fact that seizure latencies were not shortened in nonkindled animals raises an interesting possibility; that is, the period of PSI treatment and associated REM sleep loss (30 hr) may have been sufficient to produce measurable changes in seizure thresholds only in animals already disposed toward seizures. The differential effects of PSI on M M H seizure latency are not readily amenable to alternative explanations, such as inhibition of protein synthesis in peripheral tissues, because these changes were equivalent in both kindled and nonkindled animals. In summary, results of this investigation showed that protein synthesis inhibition was ineffective in reducing seizure thresholds unless it was associated with the suppression of REM sleep in animals predisposed toward seizures. Even though the integrity of REM sleep alone was not a critical determinant of seizure susceptibility, it may be concluded that the functional stability of neural systems is to some extent dependent upon REM-related anabolic activity. REFERENCES Brodsky, W., Gusatinsky, N. V.. Kogan, A. B., & Nechaeva, N. V. (1974). Variations in the intensity of 3H leucine incorporation into proteins during slow wave and paradoxical phases of natural sleep in the cat associative cortex. Doklady Akademii Nauk SSSR, 215, 748-750. Drucker-Colfn, R. R., Spanis, C, W., Cotman, C. W., & McGaugh~ J. L. (1975). Changes in protein in perfusates of freely moving cats: Relation to behavioral state. Science, 187, 963-965. Drucker-Colfn, R. R. (1981). Neuroproteins, brain excitability, and REM sleep. In W. Fishbein (Ed.), Sleep, Dreams, and Memory: Advances in Sleep Research, pp. 73-93. Flushing. N.Y.: Spectrum. Lambrey-Sakai, F. (1969). Incorporation d'un melange d'acides amines trities dans les proteines cerebrales du rat. en rapport avec la privacion de sommeil, p. 87. These de Biochemie, Universite de Lyon. Petitjean, F., Buda, C., Janin, M., David, M., & Jouvet, M. (1979). Effets du chloramphenicol sur le sommeil du chat--Comparaison avec le thiamphenicol, l'erythromycine et l'oxytetracycline. Psychopharmacology, 66, 147-153. Shouse, M. N. (1982). Acute effect of pyridoxine hydrochloride on monomethylhydrazine seizure latency and amygdaloid kindled seizure thresholds in cats. Experimental Neurology, 75, 79-88. Shouse, M. N., & Sterman, M. B. (1981). Sleep and kindling: I1. Effects of generalized seizure induction. Experimental Neurology, 71, 563-580. Sterman, M. B. (1976). Effects of brain surgery and EEG operant conditioning on seizure latency following monomethylhydrazine intoxication in the cat. Experimental Neurology, 50, 757-765. Sterman, M. B., Knauss, T., Lehman. D.. & Clemente. C. D. (1965). Circadian sleep and waking patterns in the laboratory cat. Electroencephalography and Clinical Neurophysiology, 19, 509-517. Ursin, R., & Sterman, M. B. (1981). A Manual for Recording and Scoring of Sleep Stages in the Cat. Los Angeles: Brain Information Service. UCLA.